Mineral oil composition



Patented May 17, 1938 UNITED STATES aniltgz 2,111,602 MINERAL on. COMPOSITION Ronald Bulkley,

Socony-Vaonum Oil Pitman,

N. 1., assignor to Company, Incorporated,

New York, N. Y., a corporation of New York No Drawing. Application February 18, 1936, Serial No. 64,460

6 Claims.

This invention is directed to the improvement of mineral oils used as lubricants, used in steam turbines, transformers, and the like under conditions of exposure to ,oxidation and which tend to form acids and/0r precipitates and sludges in such use. with oils both of highly refined and of more moderately refined nature, and are capable of occurrence from both long exposure at comparatively low temperature and comparatively short exposure at higher temperatures.

A' particularly delicate test for this sludgeforming and acid-forming tendency, which test is especially applicable to turbine oils, is the socalled Brown Boveri test, which may be shortly summarized as heating 200 cc. of the oil under test at 110 C. for 72 hours in the presence of a piece of copper 40 mm. x mm. x 1 mm., and

observing the effect upon the oil. Many substances are known which will largely inhibit or reduce the formation of acid .under these conditions. Scarcely any of these known inhibitors are capable of so protecting the oil that no precipitate will be formed in the Brown Boveri test. The presence of such precipitate is objectionable, and oils which are capable of withstanding the test without formation of acid and/or precipitate are regarded as highly desirable. Consequently an inhibitor or. protective agent capable of converting an oil otherwise acceptable into one which will be rated highly by the Brown Boveri test is desirable and of economic importance. It is with such an inhibitor and withoils so inhibited that this invention is concerned.

This invention has for an object the provision of oil compositions stable to a high degree against the formation of acids and/or precipitate or sludge under oxidation conditions. It has for a further object the provision of a novel reagent for accomplishing such protection, as well as the provision of a method for the recovery and preparation of that reagent. I

This'invention is based upon the discovery that there maybe extracted from solvent tar from the refining of lubricant oils, a substance which, when further refined, forms the desirable inhibiting reagent above discussed,

nsolvent refining of lubricant oils is a process wherein selectively acting solvents are made use of, by a process of extraction, to separate lubricant oils into two fractions. One is the ramnate, or refined oil, which is more highly paraffinic in nature and higher'in viscosity index, (less tendency to loss of viscosity on heating) than the raw stock. The other fraction, known as Such oxidation effects are observed solvent tar is more highly naphthenic or asphaltic in nature and consists of the fractions highly susceptible to loss of viscosity on heating which were separated from the raw stock. Additionally, this method of refining afiects the oxidation stability of products, the raflinate or refined oil being more stable than the raw stock, and the solvent tar being far more susceptible to oxidation than the raw stock from which it is derived. Yet it is known that even the refined stock from such a process or stock's refined to a similar degree by other processes, or other stocks. such as synthetic stocks, of like nature, oxidize to an undesirable degree under such rigorous conditions, and I have discovered that there may be prepared from the highly susceptible solvent tar a substance, which, when present in quite small proportions, will protect the refined stock under such conditions.

To illustrate the preparation of my novel stabilizing ingredient, I may start with; solvent tar, such as, for example, a tar prepared by the solvent refining of a naphthene base (Coastal) lubricant stock with dichlorodiethylether. This tar will then be extracted with acetone 'or methanol, and the extract, freed of-extracting solvent, treated with acid, neutralized and clay treated to form an inhibitor or stabilizer. The solvent tar was originally derived by treatment of a stock of 65 seconds Saybolt universal viscosity at 210? F. This solvent tar was countercurrently extracted with twice itsvolume of acetone, in three stages at room temperature, fill- E). About 18% of the solvent tar was so dissolved and extracted. The extract was then freed of acetone and treated with 98% sulphuric acid, at the rate of 80# acid per bbl. of extract and was neutralized and finished by being contacted with 10% of "Tonsil" clay at a'temperature of 500 F. In the above process of preparation, the volume of extraction solvent and temperature of extraction may be varied, dependent upon the nature of the tar, but normally I prefer to use from two to three volumes of solvent to' one volume of tar, and to operate at room temperature, in countercurrent fashion. Larger amounts of solvent and/or higher temperatures would be used for batch extraction. The exact amount of acid treatment must usually be determined by experiment, as too little treatment allows sludging action of the inhibitor product, and too much treatment reducesinhibiting power and allows sludging of the oil with which it is admixed. Usually, however, from '75# to 100# per bbl. of extracted material will be found suit- 55 Gravity 32.3" A. P. 1. Pour 15 F. Flash 380F. Fire 445 F. Viscosity (Saybolt U.) I

At 100 F 126" At 210 F 41.6" Sligh oxidation 2 In the following table is set forth theresults of Brown Boveri tests on the turbine oil, without inhibitor; on the same turbine 011 plus an optimum per cent of dibenzyl disulphide, a known inhibitor of high merit; and on the turbine 011 plus 2% of the novel inhibitor herein disclosed:

Broum Boveri test results color leutrali- Btock Loviration Sludge bond number Turbine oil alone 0. d 0. 96 Nil Turbine oil +.05% dibenzyl disulphide 0. 00 Present Turbine oil 4-295 of inhibitor oi this invention I 0. N N ll From the above table it will be noted that while the original oil did not form precipitate,

it did fonn acid, as indicated by the neutralization number, to an undesirable degree. Further, when stabilized against acidity by a recognized stabilizer of good ability, an undesirable precip- V itate was formed, but when stabilized with the novel ingredient herein disclosed, it was protected entirely against the formation of precipitate, and equally well protected against development of acidity.

This inhibitor may conveniently be used inthe proportion of from 1% to 5% with useful results.

ordinarily, not in excess of 2% being. preferred in admixture with oils of the types herein discussed.

I claim: "1. The method or preparing an oxidation inhibitor for use in small amounts in refined hydrocarbon oils which comprises the following steps: Extracting a solvent tar which has been separatedirom a petroleum lubricant fraction by trit'ment thereof with a solvent refining agent capable of improving viscoflty index with :from two to three volumes of acetone at a temperature of from to 80 I"., treating the material so extracted with from to 100 pounds per bbl. of 98% sulphuric acid, and neutralizing the acid treated material.

2. An antioxidant for refined petroleum lubricants comprising the material produced by extracting a solvent tar which has been separated from a petroleum lubricant fraction by treatment thereof with a solvent refining agent capable of improving viscosity index with from one to three volumes of acetone at a temperature of 1mm 70 to F., treating the material so extracted with from 75 to pounds per bbl. of 98% sulphuric acid, and neutralizing the acid treated material.

3. An antioxidant for refined petroleum lubricant oils comprising the material produced by extracting solvent tar which has been separated from a petroleum lubricant fraction by treatment thereof with a solvent refining agent capable of improving viscosity index with acetone, acid treating the extract with comparatively large amounts of strong sulphuric acid, and neutralizing the acid treated extract, which antioxidant, when present in a minor proportion in highly refined turbine oils. is capable of substantially preventing the formation of precipitate and acidity when the oil is exposed to continued elevated temperature in contact with copper.

4. A petroleum lubricant oil stable against oxidation, comprising an on not so stable, and in admixture therewith av minor proportion of a material produced by treating a lubricant petroleum fraction with a solvent refining reagent capable of increasing viscosity index to ,form a solvent tar, treating said solvent tar with acetone to form an extract, treating the extract with comparatively large amounts of-strong sulphuric acid, and neutralizing the acid treated extract.

5. A refined petroleum lubricant oil, stable against oxidation, comprising an oil not so stable and in admixture therewith not in excess of 5% of a material produced by extracting a solvent tar which has been separated from a petroleum lubricant fraction by treatment thereof with a solvent refining agent capable ofimproving viscosity index with from two to three volumes of acetone at a temperature of from 70 to 80 1"., treating the material so extracted with from 75 to 100 pounds per bbl. of 98% sulphuric acid, and neutralizing.

the acid treated material.

6. An antioxidant for refined petroleum lubricant oils comprising the material produced by extracting solvent tar which has been separated from a petroleum lubricant fraction by treatment thereof with a solvent refining agent capable of improving viscosity index with methanol, acid treating the extract with a comparatively large amount or strong sulphuric acid, and neutralizing the acid treated extract, which antioxidant, when present in a' minor proportion in highly refined turbine oils, is capable of substantially preventing the formation of precipitate and acidity when the oil is exposed to continued elevated temperature in contact with copper. v I

aomm aULxLEY. 

